Method of relief grinding cutter blades



Jan. 9, 1940. A 2,186,362

METHOD OF RELIEF GRINDING CUTTER BLADES Original Filed Feb. 11, 19:57 4 sne'ets-sneet 1 5 candee l'mog ntors B and Eras? WiZcihtIber Jan. 9, 1940. AXH. CANDEE ET AL 2,186,362

METHOD OF RELIEF GRINDING CUTTER BLADES Original Filed Feb. 11, 1937 4 Sheets-Sheet 2 \umnmmu Allan H Candee MW '35 and Ernesi W'Zdhaber A. H. CANDEE ET AL METHOD OF RELIEF GRINDING CUTTER BLADES Jan. 9, 1940.

' 4 Sheets-Sheei s Original Filed Feb. 11, 1957 AZZCU'L Candec 3nventors B and Ernesi" VViZahaZaer Jan. 9, 1940. E AL v v 2,186,362

METHOD OF RELIEF GRINDING CUTTER BLADES Original Filed Feb. 11, 1937 4 Sheets-Sheet 4 3 Allan H Candee 311mm and Ernesi mzdhczber Patented Jan. 9, 1940 V I PA ENro- F CE I Allan H. Candee, Rochester, and Ernest Wild-' haber, Irondequoit, N. 'Y., assignors to Gleason Works, Rochester, N. Y.,- a corporation of New York Original application February 11, 1937, serial N6.

125,232. Divided and this application Decemher 8, 1937, Serial No. 178,788

9 Claims.

The present invention relates to face-mill gear cutterssuch as are'employed in the cutting of spiralbevel and hypoidgears- 'Ihev invention includesboth a novel method of relief-grinding the blades orteeth of such cutters and a novel typeofbladeor-tooth. I

One purpose of the invention is to provide a bladeor tooth forface-mill gear cutters which can be..manufactured more accurately and maintained more accurate in form throughout its life than face-mill gear. cutter blades ground by the relievingprocesses heretoforein use. furtherob'ect of the invention is to provide ankimproved relieving process which will produce,

a blade ortooth. that will cut more accurately than blades orteeth as relieved by previous relieving processes. l T I Still another object of the invention is to proyideside surfaces on theteeth or blades of face-,

5Q milll gear cutters which elements.

Other objects .of the invention will be apparent hereinafter from the specificationand from the disclosure of the accompanying drawings and the 3 recital of the appended claims.-

The present application. is drawn to the relief- -contain straight-line grinding method. .The improved cutter and cut-- ting bladeare coveredby the copending application of the .presentinventors, Serial No. 125,232, filed fjebruary 11,. 1937, of which the. present application. is .a'division. I In the drawings: Figs, 1,2, 3 and 4 are, respectively; perspective plan, side'arid sectional views'of a face-'mill gear cutter blade made according to the present invention, Fig. ,4; being a section on the line 4-4 of Ei .3;

I .Fig. 5 is a fragmentary plan view ,of a face mill gear cutter head with a blademade according to the present invention mounted therein;

* Figs. 6 and 7 are a fragmentary sectional view 'anda fragmentary plan vie'w, respectively, illustreating the methodof relieving the. side surface of aIface-mill gear. cutter blade according to one 45 embodiment of this invention;

8 and 9' are a fragmentary sectional view and a. fragmentary plan view, respectively, illusti'atingthe method of relieving the side surface era" blade according to another embodiment of to this invention';'and r Figs. 10 and 11 are a fragmentary sectional view and "a fragmentary planview, respectively, illustrating the relieving of the side surface of a facemill gear cutter blade according to still further 55 embodiments of the invention.

(Cl. Si -278) In-the cutting of a spiral bevel or hypoid gear, one orboth members of the pair may be generated'. Where both members of the pair are generated, it is common practice to generate them conjugate to 'a'crown gear having teeth of theoretically straight profile andwhere only one 'member ,of the pair is generated, it is'common practice to cut the nongenerated member. of the pair with teeth of theoretically straight profile and generate the other member of the pair conjugate to this mate gear. Inthe cutting of spiral bevel or hypoid gears,,then, it isdesirable to have a face mill gear cutter which has blades of straight profilerin an-axial plane =so that :when this cutter is rotated on its axis, it may accurately trace-a surface-of; straight profile. Thus, the cutter may cut teeth of straight profile in a formcuttingoperation or may accurately represent a crown gear -ora mate gear I having teeth of straight profile in a generating operation.

Heretofore, face-mill gear cutter blades have been relief-groundby positioning'the blades in a rotary head, engaging a cylindrical grinding wheel with the blades, with the axis of the wheel lying in a plane containing theaxisof the head and inclined to the axis ofthe head at an angle approximately equal to the pressure angle of the side surfaces to be ground 'upon the blades, and rotating the head and the grinding wheel on their respective axes while effecting a relieving movement betweenthewheel and the head axially of the head. With this arrangement, however, it is not possible to grinda theoretically straight profile upon the cutting blades] Due to the relieving motion, the surface ground upon the bladesis a helicoidal surface. and a cylindrical grinding wheel cannot'contac't with such a surface along a straight line in an axial plane of the head. The surface ground upon the blades by the method heretofore employed, is .of' curved profile and varies with the diameter of the grinding wheel beingused. The profile curvature is very slight, but it nevertheless aifects'the accuracy of the tooth surfaces which are cut; a

With the present invention side surfaces are ground on the blades which are of involute helicoidal shape. Such surfaces, are of straight profile, in a plane offset from the axis of the cutter.

In an axial plane, the blades still have a slight profile curvature but only a fractional amount, a fourth or less, of what might otherwise exist on blades ground by previousprocesses. The profile curvature in the axial plane is in fact so slight, on a blade groundaccording tov thepresent invention,

as to be negligible and for' all intents'and purposes, the profile of the blades may be considered as straight also in an axial plane. Of greater importance, however, is the fact that the curvature stillrernaining is at all times constant and is not affected by the size of the grinding wheeliused or by the amount the blades have been sharpened". It is within the concept of the present invention, moreover, to grind side surfaces on face-mill gear cutter blades which will be of absolutely straight.

profile in an axial plane of the cutter. With the present invention, then, it is possible to cut gears with teeth of straight profile within an extreme degree of accuracy or to absolute accuracy if desired or to represent such gears in a generating operation.

The present invention is capable of many different embodiments. In one embodiment, a conical grinding wheel may be employed. The Wheel is positioned with its axis parallel to the axis of the head, in which the blades that are to be ground are mounted, and lying in a plane containing the axis of the head, and the wheel has its side surface dressed to a cone angle equal to the normal pressure angle of the side surfaces to be ground upon the blades. The grindingwheel and head are rotated upon their respective axes while an axial relieving movement is effected between the wheel and head; In another embodiment of the invention, a cylindrical grinding wheel is employed; This grinding wheel is positioned so that its axis is inclined to the axis of the head at an angle equal to the normal pressure angle of the side surfaces to be ground upon the blades, but the wheel is positioned so-that its axis lies in a plane offset from the axis of the head and tangent to a cylinder circumscribed about the axis of the head. In still=another embodiment of the invention, a conical. grinding wheel is employed, having a cone surface whose cone angle is equal to the normal pressure angle of the side surfaces to be ground upon the blades and this Wheel is positioned so that its axis lies in a horizontal plane offset from the horizontal plane containing the axis of the head. In a further embodiment of the invention, a conical grinding wheel is employed which has a side surface whose cone angle is less than the pressure angle of the side surfaces to be ground upon the blades and this grinding wheel is positioned in engagement with the blades so that its axis is inclined at such an angle to'the axis of the head that the side surface of the wheel will produce the desired pressure angle on the side surfaces of the blades to be ground and the wheel is at the same time positioned so that its axis lies in a plane offset from the axis of the head and tangent to a cylinder circumscribed about the axis of the head. In all of these embodiments of the invention, the actual relieving operation is effected by rotating the grinding wheel on its axis while the head rotates on its axis at a uniform velocity and while simultaneously a relative relieving movement is produced between the wheel and- I head at a uniform velocity in a direction axial of the head.

wheel with a slightly curved profile. For the outside surfaces of the blades, the grinding wheel will be dressed to have a slightly convex profile and for the inside surfaces of the blades, a slightly concaveprcfile will be used.

Reference may now be had to the drawings for a more complete description of the invention. l5-denotes a face-mill gear cutter blade relieved according tothis invention. The blade shown is intended for use in a cutter of the inserted-blade type, although the invention applies equally to cutters of the segmental type, where the blades or teeth are integral? with segments which are secured to the cutter head, and to cutters where the blades or teeth are actually integral with the cutter head itself.

The blade shown is an inside cutting blade. It

has a body portion which is adapted to be secured in a slot in the cutter head and a cutting portion which is adapted to project beyond the adjacent side face of the cutter head in the general direction of the axis of the cutter.

The front face ll of the cutting portion of the blade is sharpened with a side rake, as clearly shown in Figs. 2 and 4, to provide the inside cutting edge iii of acute angle. The top surface 19 and the side surface 20 of the blade are relieved back of the front face toprovide cutting clear-, ance. The relief on the top side of the blade may be provided in any usual or suitable manner. The present invention is concerned with the relieving of the side surfaces of the blade and particularly the side surface back of the side cutting edge. The side surface 2! of the blade, which is the non-cutting side of the blade, may be ground in any usual or suitable manner to PTO! vide the necessary clearance or, if desired, may also be ground as an involute helicoidal surface,

For the relieving operation, the blade is secured as shown in Fig. 5, in a rotary head which is provided with a plurality of bladereceiving slots 26. This head may be identical with that used for holding the blade during cutting and the blade may be secured in a slot 26 in the usual manner by a bolt which passes through the bolt opening 27 in the body portion of the blade and threads into the head.

The side 29 of the blade is ground as an involute helicoidal surface whose axis coincides preferably with the axis 28 of the cutter head 25, that is, the surface 29 is a surface such as might be produced by a straight line in a plane 29 which is tangent to a cylinder 30 that is circumscribed about the axis 28 and which is rotated about the cylinder 30 and simultaneously translated inthe direction of the axis 223 of the cylinder while remaining tangent to the cylinder. The side surface 2d! of the blade, then, contains a straight line element in any plane 29 offset from the axis 28 of the head and tangent to the cylinder 30, that is, the side surface 20 of the blade is of straight profile in such a plane offset from the cutter head axis 28. Also, the intersection of a plane perpendicular to the axis 28 of the cutter head, aplane such as shown in section in Fig. 4 or in dotted linesin Fig. 5, with the side surface 25) of the blade is an involute curve 32', that is, a curve such as might be traced by a point on a straight line lying in a plane 29 and rolling without slipping on a circle formed by the intersection of the cylinder 30 with that plane.

Various methods may be employed, as above indicated, for relief-grinding the side surface of blades according to the present invention. One method is shown in Figs: 6' and 7. Herea conical greases grinding? wheer' ernployedl This Wheel "is parallel to the axis 39 of the rotary head 40 in which the blades that are to be ground are secured. I

" To relief-grindan involute helicoidal surface on the inside of the blade'tl, the grinding wheel 35 is brought into engagement with the inside surface of the blade and rotated on its axis 38 Y ,the head. .The relative rotary and translatory :movementsare at uniform velocities and are at and at the same time the head it is rotated at a emiorm velocity on its axis 39and a relative relieving movement is produced between the head 40 and the grindingwheel 35 axially of the axis 39 and at a uniform velocity.

In Figs. 6 and '7, the grinding wheel 35 has been shown as positioned with its axis 38 lying in the same horizontal plane .42 as the axis 3% of the cutter head 40. contacts, however, with the inside surface 43 of tthe cutter blade 3'! along a straight line 44 which lies "in the plane ldoffset from the axis 39 of the cutter head and tangent to a cylinder 46' circumscribed about the axis 39 of the cutter 'lieadf Thus, as the cutter head rotates at a uniform velocity on its axis and the relative axial movement is produced between the cutter head and grinding wheel axially of the cutter head at a uniform velocity, the grinding wheel traces and grinds an involute helicoidal surface on the inside 33 of the cutter blade. This involute helicoidal' 'surface is denoted by the lines 41 and 48 in Fig. 7 "which contain-the topmost andjbottommost lines of the cutting portion of the side surface $3 of-th'eblade. The side surface 43 of the blade is, therefore, of straight profile 44 in the plane t5; In this case, the offset of the plane 45 is produced automatically without any setting adjustment and depends only upon the angle of the conical wheel and the lead of the relieving motion. i

The outsidesurface 39 of the blade 31 may also be ground 'to an'involute helicoidal profile by positioning a conical grinding wheel to engage the outside surface of the blade, by rotating the wheel on its axis, and simultaneously producing a rotary motion between the wheel and head at a uniform velocity about the axis 39 of the head and efiecting a relative movement'between the wheel and head at a uniform velocity in the direction of the axis 3901? the head. .The grinding wheel will, of course, be dressed as before so that'thefcone angle of the side surface will'equal the normal pressure angle to be ground upon the outside surface of the blade. In the drawings, only one blade has been shown for the purpose of clearness inillustration. It will be understood, however, thatthe head 48 is provided with a plurality of blade-receiving slots 53 and that a pluralityof blades may be relief-ground simultaneously by positioning them in the head Mi and effecting the required relievingmotion as each blade rotates past the grinding wheel.

Another way of reliefgrinding involute helicoidal surfaces upon the sides of faceemill gear cutter blades is shown in Figs, 8 and 9. Here a cylindrical grinding wheeltii isemployed. The

blade or blades Elto be ground'are secured in a rotary head 58 by bolts 59. The inside surfaces 69 are shown being relief ground. The grinding wheel employed is a cylindrical grinding. wheel The grinding wheel 35 'J'and:it:is='.-posltioned'so that its axis '66 is in=-' clined to the axis 61 of the head 58 at an angle equalf-to'thenormal. pressure angle of the inside surface 60'3of'the blade. "Further, the wheel'is' positioned .so that its'axis 66 lies in a plane 68 whiohjis offset-from the axis Bl of the head and is tangent to a cylinder 68 circumscribed about the axis of thehead. In the relief-grinding operation," the wheel is rotated on its axis, a relative rotary movement is produced between the-"wheel and'headiabout the axis 61 I of'the head and a "relativetaxial movement is effected between the wheel and head inthe direction of the axis 51 of suchtrates that an involute helicoidal surface is ground on the inside v6!]- of" the blade. This helicoidalrsurface is denoted by the lines 1'0 and H in Fig.;9,' which pass through the tip and bottom'of 'the cutting portion of the side surface fall of the blade 51-. .wheel 65 contacts :with this surface along the The cylindrical grinding 'head'andi-with theflaxis of the wheel lying in a plane 'foffset fromlthe axis of" the head and effecting relative rotary and translatory movemeritssuch as already "described.

. A further way of relief grinding face-mill gear cutter blades accordingtothe present invention is shown in Figs. 10 and '11. The blade to be groun'd'i's denotedv at .15. It is secured in a rotary head'lby a bolt 11:. 'Again the invention is illustratediri connection with the grinding of the 'insidesurface ofthe blade. The grinding wheel used'is a conical grinding wheel 80 having its/operating side surface 8| dressed at an angle to produce the correct pressure angle on the inside surface 82 of the blade when the grinding wheel istpositioned so that 'its'a'xis83 is. parallel to the axis 84 of thehead '16.

The embodiment illustrated in Figs. 10' and 11 distinguishes from the embodiment shown in Figs. 6 and '7 in the respect that the wheel is positioned so that its axis 83 lies in a horizontal plane 85 which is offset from the horizontal plane 86 that contains the axis 84 of the cutter head and in the respect that the line of contact between theblade surface and the wheel remains continuously in the same offset plane though the wheel diameter be decreased by repeated dressings. The relief-grinding operation itself is effected, as before; the grinding wheel is rotatedon its axis 83 in engagement with the insidefsurfaceBZ of the blade, relative rotary movement is produced between the wheeland bladeabout the axis 84 of the cutter head and simultaneously a relative translatory movement is produced between the wheel and blade in the direction of theaxis 84 of the head. The .relative rotary and translatory movements are efblade may be ground in a manner similar to that just described by positioning the grinding wheel to engage the outside surface of the blade and effecting relative rotary and translatory movements such as described.

There m a still further way of grinding involute helicoidal surfaces upon cutter blades. A conical grinding wheel may be employed, but the grinding wheel may be positioned, as shown in dotted lines in- Fig. 10, so that its axis 95 is inclined to the axis 84 of the cutter. Here the grinding wheel 96 has its operating side surface 9'! dressed to an angle less than the pressure angle of the inside surface 82 of the blade and the prop-er pressure angle is obtained by inclining the wheel to the axis of the cutter head.

In this case, as in the case just described, the grinding. wheel is positioned with its axis 95 lying in a plane, such as the plane 85, offset from the axis 84 of the cutter head and tangent to a cylinder, such as the cylinder? just described, circumscribed about the axis of the cutter head.

The relieving operation is efiected, as before, by

rotating the grinding wheel on its axis, while rotating the head on its axis or otherwise producing a relative rotary movement between the wheel and head about the axis of the head and by effecting a relative translatory movement be-- tween the wheel and head in the direction of the axis 84 of the head. The wheel, as before, will contact with the relieved side surface of the blade along a straight line lying in a planeofiset from the axis of the head and the blade will be of straight profile in this plane. a

In all of the embodiments of the invention described, the grinding wheel is of straight profile and the surface ground upon the blade is of straight profile in a plane offset from the axis of the cutter head. In a plane radial of the axis of the cutter head, the blades are of slightly curved profile. This curvature, however, is so slight that it is negligible. If it is desired, however, for any reason, to grind a truly straight profile on the cutter blade in an axial plane of the cutter head, this can stillbe done by dressing the grinding wheel with a slightly curved profile. For the grinding of the inside surfaces of the cutter blades, the wheel should be dressed to a slightly concave profile and for the grinding of the outside surfaces of the blades, the wheel should be dressed to a slightly convex profile.

In any of the embodiments of the invention illustrated, the blades to be ground may be circularly arranged in the cutter head and the axial relieving movement effected as each blade is moved past the grinding wheel or the blades may be helically arranged upon a rotary head and the relieving effected by imparting only one axial movement as a group of blades pass across the wheel. For the circular arrangement, a machine such as illustrated in the patent to James E". Gleason, No. 1,285,124 of" November 19, 1918,

maybe employed and for the helical'arrangement, a machine such as illustrated in the Durkan Patent No. 1,906,845 of May 2, 1933, may be employed, the grinding wheel or wheels for grinding the side surfaces of the blades being arranged in either case according to the present invention.

The invention has been illustrated, moreover, in connection. with the grinding of blades intended for use in cutters of the inserted-blade type. It will be understood, however, that the invention may also be employed for relief-grinding of the cutting teeth or blades of segments intended for use upon a face-mill gear cutter of the segmental type. The invention may also be employed in the relief-grinding of the teeth or blades of a face-mill gear cutter in which the blades are integral with the body of the cutter head.

It will be understood, further, that while a number of different embodiments of the invention have been illustrated, the invention is capable of still further modification and this application is intended to cover any variations, uses, or adaptations of the invention and including such departures from the present disclosure as come Within known or customary practice in the gear art and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described our invention, what we claim is:

1. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel, which has a conical operating surface, with the blade so that. the axis of the wheel is parallel to the axis of the head and the wheel contacts with a side surface of the blade along a line lying in a plane tangent to a cylinder coaxial with the head, and rotating the wheel and head on their respective axes while producing a relative. movement between the wheel and head axially of the head in time with the rotation of the head.

2. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel, which has a cylindrical operating surface, with the blade so that the axis of the wheel is inclined to the axis of the head in accordance with the normal pressure angle of the side surface to be ground upon the blade and so that the axis of the wheel lies in a plane offset from the axis of the head, and rotating the wheel and head on their respective axes while producing a relative movement between'the wheel and head axially of the head.

3. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel with the blade so that the axis of the wheel is inclined to the axis of the head and lies in a plane offset from the axis of the head, and rotating the wheel and head on their respective axes while producing a relative movement between the wheel and head axially of the head.

4. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel with the blade so that the wheel contacts with the side surface to be ground along a line lying in a plane offset from the axis of the head. and tangent to a cylinder circumscribed about the axis of the head and roa rotary grinding wheel with the head so that the wheel contacts the side surface to be ground along a straight line lying in a plane offset from the axis of the head and tangent to a cylinder circumscribed about the axis of the head, and rotating the wheel onits axis, while producing a relativerotary motion at a uniform velocity between the wheel and head about the axis of the head and effecting a relative movement of translation at a uniform velocity between the. wheel and head in the direction of the axis of the head.

6. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel, which has a conical operating surface, with the blade so that the wheel contacts with a side surface of the blade along a line lying in a plane offset from the axis of the head and tangent to a cylinder circumscribed about th axis of the head and the axis of the wheel is parallel to the axis of the head and lies in a plane containing the axis of the head, and rotating the wheel and head on their respective axes while effecting a relative movement between the wheel and head in the direction of the axis of the head in time with the rotation of the head.

7. The method of relieving a side surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel which has a conical opcrating surface, with the blade so that the wheel contacts with a sidesurface of the blade alon g'a line lying in a-plane offset from the axis of the head and tangent to a cylinder circumscribed "about the axisof the head and the axis of the wheel is inclined to the axis of the head and lies in a plane offset from the axis of the head, and rotating the wheel and head on their respective axes while effecting a relative movement between the wheel and head in a direction axial of the head in time with the rotation of the head.

8. The method of relieving aside surface of a face-mill gear cutter blade which comprises mounting the blade in a rotary head, engaging a rotary grinding wheel, whose sidesurface is of curved profile, with the blade so that the wheel contacts with the side surface, which isto'be ground, along a line lying in a plane offset-from the axis of the head and tangent to a cylinder circumscribed about the axis of the head, and.

the axis of the'head and tangent to a cylindercircumscribed about the axis of the head, and rotating the, wheel and head on their respective axes while producing a relative movement between the wheel and head axially of the head.

ERNEST W'JLDHABER. 

